The small skirmishes between security forces and demonstrators unfolded along streets adjacent to Tehran University, the capital's main institution of higher learning. Protests occurred despite opposition leaders Mir Hossein Mousavi and Mehdi Karroubi having called off the demonstrations, apparently concerned that the official crackdown would be too harsh.

Both men ran and lost against President Mahmoud Ahmadinejad a year ago Saturday in an election landslide immediately derided as fraudulent by the nation's reformist opposition and suspect by most independent observers.

The vote sparked a months-long, largely peaceful anti-government uprising quashed by Iranian authorities using mostly non-lethal force, mass imprisonments and a relentless media campaign on state-controlled television and radio depicting the opposition as foreign dupes.

Dozens were killed in the crackdown and thousands imprisoned, though many were released on hefty bail.

In Saturday's clashes, at least five young men were arrested, handcuffed and hauled away by militiamen and uniformed officers.

Security forces opened fire with paint guns and rubber bullets, one striking the ear of a young man.

Police and demonstrators played cat-and-mouse through side streets, and pro-government militiamen could be seen pummeling protesters as cries of "Death to the dictator" rang out.

An opposition supporter said in a phone conversation that police and demonstrators also were clashing in the side streets adjacent to Azadi Avenue. Forces had cordoned off the area to disperse a gathering and were using paint guns to frighten away opposition supporters.